The present invention relates to a process for preparing a 1,3-dihaloalkene compound, such as a 1,3-dichloropropene or a homolog thereof, from the corresponding allylic geminal dihalide compound, such as a 3,3-dihalopropene or homolog thereof, by treatment with an alumina, silica, or zeolite catalyst.
Many different methods for producing 1,3-dichloropropenes have been suggested, for example, by reacting 1,2-dichloropropane with a gas containing oxygen in the presence of a catalyst containing CuCl.sub.2, LiCl and ZnCl.sub.2 at 470.degree. C. to 490.degree. C.: by dehydrochlorination of 1,2,3-trichloropropane in the presence of oxygen or a halogen; by contacting 1,2-dichloropropane with chlorine to effect both chlorination and dechlorination reactions; or by mixing 1,2-dichloropropane with allyl chloride and/or 1-chloropropene and reacting with chlorine at high temperature. However, all these processes are rather complicated, energy-consuming an/or inconvenient.
1,3-Dichloropropenes have been prepared by isomerization of 3,3-dichloropropene in the presence of hydrogen chloride. This isomerization is also known from Japanese Patent No. 80-69,523 to take place in the presence a catalytic amount of a zinc, iron, copper, tin, titanium or vanadium salt. The isomerization catalyst is suspended in the reaction mixture and the reaction is carried out at a temperature between 0.degree. C. and 200.degree. C. This disclosed process of rearranging 3,3-di-chloropropene to 1,3-dichloropropenes is, however, rather inconvenient because the finely suspended catalyst is difficult to remove from the reaction mixture after completion of the rearrangement process.
The production of 1,3-dichloropropenes and their homologs starting from 3,3-dichloropropene and its homologs is advantageous because 3,3-dichloropropene and its homologs do not have a significant commercial use and are available. 3,3-Dichloropropene itself is produced as a by-product in the important commercial process of producing allyl chloride by chlorinating propylene. In the past, the 3,3-dichloropropene produced has usually been incinerated.
It is known in the art, however, that both the cis and trans isomers of 1,3-dichloropropene have many useful properties. For example, it is known from published German Patent Application No. 1,210,618 that these compounds are useful as nematocides. They are also useful as insecticides. These and other compounds produced by the invention are also known to be useful as monomers in the production of plastics and resins and as chemical intermediates. Because of these useful properties, much effort has been spent to produce such compounds in the recent years.
Therefore, it remains highly desirable to provide a simple and high yield process for producing 1,3-dihalopropenes and their homologs from 3,3-dihalopropenes and their homologs.